The woven fabric used for the outside surface or inside surface of a garment such as a down jacket or a fake down jacket is required to have a moderately low air permeability to ensure that the down or the fake down in the garment can be prevented from coming out and that the garment can be deformed to be inflated and deflated in response to the air coming in and out. To achieve a moderately low air permeability, methods of enhancing the weave density of the fabric and calendering the fabric, to compress the fibers, for lessening the inter-thread clearance are known (JP 3-241078 A, JP 2005-48298 A and JP 2004-339672 A). Further known are methods of coating or laminating a fabric with a continuously microporous film over the entire surface and a method of partially coating a fabric using a gravure roll or the like at a surface cover rate of 50 to 90% (JP 5-176832 A and JP 2007-56414 A).
The methods of controlling a low air permeability by enhancing the weave density and calendering have fundamental problems that the capability of smoothly undergoing the process is very low since yarn breaking frequently occurs and that the productivity remains low since the weaving speed is low, especially when a high-density thin woven fabric is produced by using yarns with a small fineness as required for recent down jackets. Further, even if the fabric obtained has a moderately low permeability in the initial state, it is likely to be difficult to maintain the initial low air permeability, since the inter-thread clearance is spread with the lapse of time by such forces as friction, bending and expansion/contraction in daily use accompanying folding, washing, etc. Especially a thin woven fabric composed of yarns with a small fineness is likely to increase in air permeability as time passes, and down or fake down is likely to come out. Further, if the density of the woven fabric is enhanced, the force of binding yarns together increases, causing the tear tenacity to decline, and especially in a thin woven fabric, the decline of tear tenacity is likely to pose a serious problem since the yarn tenacity is low.
On the other hand, in the method of coating or laminating the fabric with a continuously microporous film, the micropores are too small to achieve an adequate air permeability. Especially when a thin woven fabric preferred for down jackets is coated or laminated with a film, the film is likely to harden the fabric hand and to have a larger weight and, therefore, such a method is not suitable for a thin woven fabric. Further, since coating or lamination perfectly fixes the yarns in their mutual relation, the force for binding the yarns together increases as in the case of enhancing the density of the woven fabric, and the tear tenacity declines. Furthermore, according to the method of partially coating the fabric with a resin at a surface cover rate of approx. 50 to approx. 90% using a gravure roll or the like, the decline of tear tenacity and the hardening of fabric hand can be prevented while the low air permeability is maintained if the woven fabric has a medium to large thickness. However, if the woven fabric has a small thickness, the hand peculiar to the fabric may be impaired and the fabric may become heavy as in the case of full surface coating. Furthermore, a high surface cover rate can lower the tear tenacity. Therefore, it is not practical to employ this method for a thin woven fabric.
In view of these situations, it could be helpful to provide an excellent light-weight down-proof woven fabric having not only a moderately low air permeability that can prevent the down or the fake down in a garment from coming out and allows the garment to be easily deformed, i.e., inflated and deflated in response to the air coming in and out, but also the capability of preventing temporal deterioration, i.e., to inhibit the rise of air permeability, further having a practically endurable sufficient tear tenacity and not impairing the hand peculiar to the fabric.